Ignition Coil for Internal Combustion Engine

ABSTRACT

An object of the present invention is to provide an ignition coil for use in an internal combustion engine, offering improved water drainage performance, while achieving high waterproof performance with controlled entry of water in a plug hole. A high-voltage generating section  3  that generates a high voltage is housed inside a coil case  4 . A plug hole seal  5  closes an opening in a plug hole  2  in which an ignition plug  21  is mounted. The ignition coil further includes a space portion  6  placed on an outer side portion of the high-voltage generating section  3  and an air path  9  for venting air between the space portion  6  and the plug hole  2 . The space portion  9  has an open lower surface (an entirely open surface facilitates demolding).

TECHNICAL FIELD

The present invention relates to ignition coils for use in internalcombustion engines, the ignition coils supplying high voltages forcausing spark discharges to occur at ignition plugs of internalcombustion engines. More specifically, the invention relates to anignition coil for use in an internal combustion engine, suitable forwaterproofing of a plug hole.

BACKGROUND ART

In conventional ignition coils for use in internal combustion engines,the inside of a plug hole communicates with an outside atmosphericpressure side via an air path disposed at a boundary between an outerperiphery of the ignition coil and a plug hole seal. This is done todischarge/take air from/to the inside of the plug hole to facilitateremoval of the ignition coil, the air being produced when thetemperature inside the plug hole changes or the ignition coil is removedor reinstalled. A change in ambient temperature or the internalcombustion engine being splashed with water, however, causes thetemperature of the plug hole to be reduced, resulting in a change inpressure inside the plug hole. Thus, to achieve equilibrium with theoutside air, a negative pressure is created to draw the outside air in.Then, the negative pressure may cause water to enter the plug hole fromthe outside via an opening in the air path on the atmospheric side.

A known arrangement includes a pool section (water retention chamber)for storing therein water that enters the air path (see, for example,Patent Document 1). Water entering from the outside is retained in thepool section and thus prevented from entering the plug hole.

PRIOR ART LITERATURE Patent Document

-   Patent Document 1: JP-2008-60228-A

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

The arrangement disclosed in Patent Document 1 has a small air path(vent port) formed at a position before (on the atmospheric side) thepool section for storing therein water, in order to ensure that waterenters the pool section less easily. The structure makes water less easyto enter the pool section because of the small air path on the one hand;on the other hand, it makes water once in the pool section less easy tobe discharged therefrom. Under repetitive environmental conditions inwhich the ignition coil is temporarily totally submerged in water,therefore, the related-art arrangement, while achieving high waterproofperformance with controlled entry of water in the plug hole, offers onlypoor water drainage performance and may cause water held in the poolsection to enter the plug hole.

It is an object of the present invention to provide an ignition coil foruse in an internal combustion engine, offering improved water drainageperformance, while achieving high waterproof performance with controlledentry of water in a plug hole.

Means for Solving the Problem

(1) To achieve the foregoing object, an aspect of the present inventionprovides an ignition coil for an internal combustion engine. Theignition coil includes: a coil section for generating a high voltage; acoil case for housing therein the coil section; a plug hole seal forclosing an opening in a plug hole in which an ignition plug is disposed;a space portion divided by an outer peripheral wall disposed on an outerside portion of the coil case; and an air path for venting air betweenthe space portion and the plug hole. The space portion is connected, ata first end portion thereof on a side opposite to a side of a second endportion thereof on which the ignition plug is connected, via a smallhole to a first end of the air path having a second end communicatingwith the plug hole, and the second end portion of the space portion onthe side on which the ignition plug is connected is open to anatmosphere through an opening having a path area larger than a path areaof the small hole.

Such arrangements can improve water drainage performance, whileachieving high waterproof performance with controlled entry of water inthe plug hole.

(2) In the arrangements of (1) above, preferably, the space portion andthe air path are formed integrally with the coil case. The ignition coilfurther includes a sealing member for sealing the first end portion ofthe space portion on the side opposite to the side of the second endportion on which the ignition plug is connected, the sealing memberforming part of the air path connecting the plug hole to the spaceportion via the small hole.

(3) In the arrangements of (1) above, preferably, the air path is formedintegrally with the coil case, and the space portion is formed by a sidecase fixed afterwards to the coil case.

(4) In the arrangements of (1) above, preferably, the air path isdisposed within a central ⅓ portion in a width direction of the spaceportion.

(5) In the arrangements of (2) above, preferably, the space portion hasthe small hole formed, at the first end portion on the side opposite tothe side of the second end portion on which the ignition plug isconnected, to extend in a direction in which the ignition plug isinserted into the plug hole, the sealing member for covering the airpath and the small hole forms a horizontal path connecting the air pathand the small hole, and the air path extends in a direction in which theignition coil is inserted into the plug hole and has an end portionconnected to the plug hole.

(6) In the arrangements of (2) above, preferably, the air path has astepped or tapered portion at a connection to the small hole to therebyhave a cross-sectional area larger than a cross-sectional area of thesmall hole.

(7) In the arrangements of (2) above, preferably, a protrusion is formedof the coil case to protrude toward the sealing member at anintermediate horizontal portion which is formed at the stepped ortapered portion of the air path.

(8) In the arrangements of (1) above, preferably, a portion around aconnection of the air path to the plug hole has a protrusion formedintegrally with the coil case to extend toward the side opposite to theside on which the ignition plug is connected.

(9) In the arrangements of (1) above, preferably, the outer peripheralwall for forming the space portion has a protrusion protruding from theouter peripheral wall so as to cover an area around the opening in thespace portion.

Effect of the Invention

The aspect of the present invention can improve water drainageperformance, while achieving high waterproof performance with controlledentry of water in the plug hole.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing arrangements of an ignitioncoil for use in an internal combustion engine according to a firstembodiment of the present invention.

FIG. 2 is another cross-sectional view of the ignition coil shown inFIG. 1.

FIG. 3 is a cross-sectional view taken along line A-A of FIG. 2.

FIG. 4 is a cross-sectional view showing arrangements of an ignitioncoil for use in an internal combustion engine according to a secondembodiment of the present invention.

FIG. 5 is a cross-sectional view showing arrangements of an ignitioncoil for use in an internal combustion engine according to a thirdembodiment of the present invention.

FIG. 6 is a cross-sectional view showing arrangements of an ignitioncoil for use in an internal combustion engine according to a fourthembodiment of the present invention.

FIG. 7 is a cross-sectional view showing arrangements of an ignitioncoil for use in an internal combustion engine according to a fifthembodiment of the present invention.

MODES FOR CARRYING OUT THE INVENTION

Arrangements of an ignition coil for use in an internal combustionengine according to a first embodiment of the present invention will bedescribed below with reference to FIGS. 1 to 3.

FIG. 1 is a cross-sectional view showing arrangements of the ignitioncoil for use in an internal combustion engine according to the firstembodiment of the present invention. FIG. 2 is another cross-sectionalview of the ignition coil shown in FIG. 1. FIG. 3 is a cross-sectionalview taken along line A-A of FIG. 2.

In FIG. 1, an internal combustion engine ignition coil 1 is anindependent ignition type mounted in a plug hole 2 of each cylinderformed in a cylinder head of an internal combustion engine and directlycoupled to an ignition plug 21. The internal combustion engine ignitioncoil 1 includes a connector 16. An external battery supplies electricpower to an igniter 17 or a coil section 3 inside the internalcombustion engine ignition coil 1 via an internal terminal of theconnector 16. An external engine control unit (ECU) supplies an ignitionsignal to the igniter 17 inside the internal combustion engine ignitioncoil 1.

The ignition coil 1 includes the igniter 17 that operates according toan ignition signal from the ECU, the coil section 3, a coil case 4, anda plug hole seal 5. The coil section 3 includes, for example, a primarycoil, a secondary coil, and a laminated core and generates a highvoltage. The coil case 4 formed of a thermoplastic resin houses thereinthe igniter 17 and the coil section 3. The plug hole seal 5 is disposedbetween the coil case 4 and the plug hole 2 to thereby close an openingin the plug hole 2.

The plug hole 2 is formed in a cylinder head CH of the internalcombustion engine for each cylinder. The ignition plug 21 is screwedinto the cylinder head CH at a lower portion of the plug hole 2.

The coil case 4 has a lower portion sealed with a metal terminal 19. Thecoil section 3 is inserted in the coil case 4. A pin 18 is fixed in asecondary bobbin of the coil section 3 and connected to the secondarycoil. The pin 18 is formed, for example, of phosphor bronze and has aspring property. With the coil section 3 inserted in the coil case 4,the pin 18 has an end portion in contact with the terminal 19 and isconductive because of its spring property. An insulating resin 8, suchas an epoxy resin, is packed inside the coil case 4 to thereby seal theigniter 17 and the coil section 3.

The plug hole seal 5 is attached to the lower portion of the coil case4. The plug hole seal 5 is formed of, for example, silicone rubber. Theplug hole seal 5 extends in a cylindrical shape downwardly in the figureand is inserted in an electrode terminal at an upper portion of theignition plug 21. A metal spring 20 is inserted inside the cylindricalspace in the plug hole seal 5. The metal spring 20 thereby conductselectrically the terminal 19 with the electrode terminal at the upperportion of the ignition plug 21, so that a high voltage pulse generatedat the coil section 3 can be supplied to the ignition plug 21.

As shown in FIG. 2, a mounting portion 4TB is integrally formed with aside portion of the coil case 4. Meanwhile, a mounting seat ZA isintegrally formed with the cylinder head CH at an upper portion of thecylinder head CH. The mounting portion 4TB is fixed to the mounting seatZA with, for example, a bolt BT, so that the ignition coil 1 is fixed tothe upper portion of the cylinder head CH.

A space portion 6 and an air path 9 are integrally formed on an outerside portion on the right in the figure of the coil case 4. The spaceportion 6 is divided by an outer peripheral wall disposed on the outerside of the coil case 4. The space portion 6 and the air path 9communicate with each other at upper portions thereof. Specifically, thespace portion 6 is connected to an upper end portion of the air path 9through a small hole at an end portion on a side opposite to a side onwhich the ignition plug is connected. The term “small hole”, as usedherein, refers to a rectangular hole denoted by reference numeral 9 inFIG. 3. The space portion 6 is shaped like a glass turned upside down tohave an “open” lower surface (an entirely open surface facilitatesdemolding). As will be described later with reference to FIG. 3, thespace portion 6 is a path having a cross-sectional area larger than thatof the air path 9. Specifically, the space portion 6 has an end portionon the side on which the ignition plug is connected, the end portionbeing open to the atmosphere through an opening having a larger patharea than the abovementioned small hole.

The plug hole seal 5 has a small through hole 5HO formed therein. Thecoil case 4 has an outer surface having a groove portion 4GR formedtherein. With the plug hole seal 5 mounted on the lower portion of thecoil case 4, the groove portion 4GR has an upper portion communicatingwith the air path 9 and a lower portion communicating with the throughhole 5HO in the plug hole seal 5. Though being a tiny groove that is,for example, 0.8 mm wide and 0.4 mm deep, the groove portion 4GRmaintains a groove form capable of communicating between the air path 9and the through hole 4HO even with the plug hole seal 5 mounted on thelower portion of the coil case 4. In a condition in which the ignitioncoil 1 is fixed on the upper portion of the cylinder head CH, thethrough hole 5HO communicates with the plug hole 2.

Thus, a vent path between the plug hole 2 and the outside air is inorder of the space portion 6, the air path 9, the groove portion 4GR,the through hole 5HO, and the plug hole 2.

If the ignition coil 1 is splashed with water and totally submerged inwater temporarily, the cylinder head CH is cooled to reduce atemperature of the plug hole 2. Because of a resultant change inpressure inside the plug hole 2, a negative pressure is created to drawoutside air in to thereby achieve equilibrium. This negative pressurecauses water to attempt to enter the plug hole 2; however, the spaceportion 6, being shaped like a glass turned upside down, retains airthereinside even with the ignition coil 1 totally submerged in water. Byhaving a volume of the space portion 6 larger than a volume contractedas a result of the temperature change in the plug hole, a level of waterinside the space portion 6 does not increase up to an inlet (the upperportion of the air path 9) of the air path 9 that is connected to theplug hole, so that no water enters the plug hole. The space portion 6has a volume of, for example, 4 cc. Meanwhile, the plug hole 2 has avolume of about 40 cc. The volume of the plug hole contracted as aresult of the temperature change is, in this case, about 2 cc and thusthe volume of the space portion 6 is larger than the contracted volume(2 cc).

The space portion 6 has the “open” lower surface (the entirely opensurface facilitates demolding). If the water level around the ignitioncoil 1 is equal to, or lower than, the lower surface of the spaceportion 6, therefore, water drawn up into the space portion 6 by anegative pressure created in the plug hole is instantaneouslydischarged, which results in improved water drainage performance.Consequently, even under repetitive environmental conditions in whichthe ignition coil 1 is totally submerged in water temporarily, entry ofwater in the plug hole can be prevented.

If a vehicle moves with water retained in the space portion 6, the waterinside the space portion 6 moves and splashes. By setting the air path 9within a central ⅓ portion in a width direction of the space portion 6as shown in FIG. 3, however, the splashed water can be prevented fromeasily entering the air path 9. The water splashes to follow a path asindicated by an arrow in FIG. 3. The arrow path is oriented from a lowerportion of the space portion 6 toward an upper portion thereof. Water,if hitting and splashing against a short side wall of the space portion6, flies onto positions away from the central portion of the spaceportion 6, so that the splashed water can be prevented from easilyentering the air path 9 by setting the air path 9 within a central ⅓portion in the space portion 6.

As described heretofore, even under repetitive environmental conditionsin which the ignition coil is totally submerged in water temporarily,the arrangements according to the present embodiment achieve highwaterproof performance with controlled entry of water in the plug holeand offer high water drainage performance because of the open lowersurface (the entirely open surface facilitates demolding) of the spaceportion on a side of the coil.

Arrangements of an ignition coil for use in an internal combustionengine according to a second embodiment of the present invention will bedescribed below with reference to FIG. 4.

FIG. 4 is a cross-sectional view showing arrangements of the ignitioncoil for use in an internal combustion engine according to the secondembodiment of the present invention. Like parts are identified by thesame reference numerals as those used in FIGS. 1 to 3.

In the present embodiment, a coil case 4A used for an ignition coil 1Ais shaped differently from the coil case 4 shown in FIG. 2 in thefollowing points. Specifically, the coil case 4A forms a space portion6A and an air path 9A. The space portion 6A has an air path inlet (smallhole) 10 formed at an upper portion thereof. The air path inlet 10 andthe air path 9A each have an open upper portion. This opening (theopening on an end portion of the space portion on a side opposite to aside on which an ignition plug is connected) is sealed with a sealingmember 7 formed of an elastic material. The sealing member 7 has anupper portion cast in an insulating resin 8. The sealing member 7 formspart of the air path 9A that connects a plug hole and the space portion6A via the abovementioned small hole (air path inlet 10). The air path9A is formed so as to extend from the space portion 6A verticallyupwardly, then horizontally, and finally vertically downwardly.Specifically, the sealing member 7 that covers the air path 9A and thesmall hole (air path inlet 10) forms a horizontal path that connects theair path 9A and the small hole (air path inlet 10). The air path 9Aextends in a direction in which the ignition coil is inserted into theplug hole and has an end portion connected to the plug hole 2. Otherarrangements are the same as those shown in FIGS. 1 to 3.

Even under repetitive environmental conditions in which the ignitioncoil is totally submerged in water temporarily, the arrangementsaccording to the present embodiment also achieve high waterproofperformance with controlled entry of water in the plug hole and offerhigh water drainage performance because of the open lower surface (theentirely open surface facilitates demolding) of the space portion on aside of the coil.

Arrangements of an ignition coil for use in an internal combustionengine according to a third embodiment of the present invention will bedescribed below with reference to FIG. 5.

FIG. 5 is a cross-sectional view showing arrangements of the ignitioncoil for use in an internal combustion engine according to the thirdembodiment of the present invention. Like parts are identified by thesame reference numerals as those used in FIGS. 1 to 3.

In the present embodiment, a coil case 4B used for an ignition coil 1Bis shaped differently from the coil case 4 shown in FIG. 2 in thefollowing points. Specifically, while the coil case 4B forms a spaceportion 6, a side case 15 separate from the coil case 4B is tightlyfixed afterwards to the coil case 4B through, for example, bonding, tothereby form a space portion 6B. This makes the space portion 6B havingan even larger volume. Other arrangements are the same as those shown inFIGS. 1 to 3.

Even under repetitive environmental conditions in which the ignitioncoil is totally submerged in water temporarily, the arrangementsaccording to the present embodiment also achieve high waterproofperformance with controlled entry of water in the plug hole and offerhigh water drainage performance because of the open lower surface (theentirely open surface facilitates demolding) of the space portion on aside of the coil.

Arrangements of an ignition coil for use in an internal combustionengine according to a fourth embodiment of the present invention will bedescribed below with reference to FIG. 6.

FIG. 6 is a cross-sectional view showing arrangements of the ignitioncoil for use in an internal combustion engine according to the fourthembodiment of the present invention. Like parts are identified by thesame reference numerals as those used in FIGS. 1 to 4.

In the present embodiment, a coil case 4C used for an ignition coil 1Cis shaped differently from the coil case 4 shown in FIG. 2 in thefollowing points. Specifically, the coil case 4C forms a space portion6C and an air path 9C. The space portion 6C has an air path inlet (smallhole) 10 formed at an upper portion thereof. The air path inlet 10 andthe air path 9C each have an open upper portion. In addition, the airpath inlet 10 is stepped. Should a negative pressure be created in theplug hole with water droplets affixed to the air path inlet 10, thewater droplets go up above the air path inlet 10; as the water dropletsgo up, the air path cross-sectional area increases, causing the waterdroplets to be thin and eventually drop. Instead of being stepped, theair path inlet 10 may be tapered.

The coil case 4C forms a protrusion 11 extending upwardly at anintermediate horizontal portion of the air path. The protrusion 11functions as an elevated breakwater to prevent water from climbing overeasily. The protrusion 11 protrudes toward a sealing member 7.

The abovementioned opening is sealed with the sealing member 7 formed ofan elastic material. The sealing member 7 has an upper portion cast inan insulating resin 8. The air path 9B is formed so as to extend fromthe space portion 6B vertically upwardly, then horizontally, and finallyvertically downwardly.

A protrusion 13 is disposed around an outlet 12 at a lower portion ofthe air path 9C. This makes a zone in which water can be held, so thatwater can be prevented from easily entering the outlet 12 of the airpath. The protrusion 13 is disposed around a connection of the air path9C to the plug hole and formed integrally with the coil case.Additionally, the protrusion 13 protrudes in a direction opposite to theside on which the ignition plug is connected. Other arrangements are thesame as those shown in FIGS. 1 to 3.

Even under repetitive environmental conditions in which the ignitioncoil is totally submerged in water temporarily, the arrangementsaccording to the present embodiment also achieve high waterproofperformance with controlled entry of water in the plug hole and offerhigh water drainage performance because of the open lower surface (theentirely open surface facilitates demolding) of the space portion on aside of the coil.

Arrangements of an ignition coil for use in an internal combustionengine according to a fifth embodiment of the present invention will bedescribed below with reference to FIG. 7.

FIG. 7 is a cross-sectional view showing arrangements of the ignitioncoil for use in an internal combustion engine according to the fifthembodiment of the present invention. Like parts are identified by thesame reference numerals as those used in FIGS. 1 to 4.

In the present embodiment, a coil case 4D used for an ignition coil 1Dis shaped differently from the coil case 4A shown in FIG. 4 in thefollowing points. Specifically, an outer peripheral wall that forms aspace portion 6A of the coil case 4D has a protrusion 14 extending in aperpendicular direction. The protrusion 14 protrudes from the outerperipheral wall for forming the space portion 6A so as to cover an areaaround an opening in the space portion 6A. Should the ignition coil 1Dbe splashed with water under high pressure during high-pressure washing,the protrusion 14 prevents water from gathering at the underside of thespace portion 6A, thus adequately controlling entry of water from theopen lower surface. The protrusion 14 may be high enough to be disposedon the outer peripheral wall.

Even under repetitive environmental conditions in which the ignitioncoil is totally submerged in water temporarily, the arrangementsaccording to the present embodiment also achieve high waterproofperformance with controlled entry of water in the plug hole and offerhigh water drainage performance because of the open lower surface (theentirely open surface facilitates demolding) of the space portion on aside of the coil.

It is noted that the present invention is directed to bothwhat-is-called a plug top type ignition coil having the coil section atthe upper portion of the plug hole and what-is-called a plug hole typeignition coil having the coil section inside the plug hole.

DESCRIPTION OF REFERENCE NUMERALS

-   1 Ignition coil for internal combustion engine-   2 Plug hole-   3 Coil section-   4 Coil case-   5 Plug hole seal-   6 Space portion-   7 Sealing member-   8 Insulating resin-   9 Air path-   10 Air path inlet-   11 Protrusion at air path horizontal section-   12 Air path outlet-   13 Protrusion near air path outlet-   14 Protrusion extending perpendicularly from outer peripheral wall-   15 Side case-   16 Connector-   17 Igniter-   18 Pin-   19 Terminal-   20 Spring-   21 Ignition plug

1. An ignition coil for an internal combustion engine, the ignition coilcomprising: a coil section for generating a high voltage; a coil casefor housing therein the coil section; a plug hole seal for closing anopening in a plug hole in which an ignition plug is disposed; a spaceportion divided by an outer peripheral wall disposed on an outer sideportion of the coil case; and an air path for venting air between thespace portion and the plug hole, wherein the space portion is connected,at a first end portion thereof on a side opposite to a side of a secondend portion thereof on which the ignition plug is connected, via a smallhole to a first end of the air path having a second end communicatingwith the plug hole, and the second end portion of the space portion onthe side on which the ignition plug is connected is open to anatmosphere through an opening having a path area larger than a path areaof the small hole.
 2. The ignition coil for an internal combustionengine according to claim 1, wherein the space portion and the air pathare formed integrally with the coil case, the ignition coil furthercomprising: a sealing member for sealing the first end portion of thespace portion on the side opposite to the side of the second end portionon which the ignition plug is connected, the sealing member forming partof the air path connecting the plug hole to the space portion via thesmall hole.
 3. The ignition coil for an internal combustion engineaccording to claim 1, wherein the air path is formed integrally with thecoil case, and the space portion is formed by a side case fixedafterwards to the coil case.
 4. The ignition coil for an internalcombustion engine according to claim 1, wherein the air path is disposedwithin a central ⅓ portion in a width direction of the space portion. 5.The ignition coil for an internal combustion engine according to claim2, wherein the space portion has the small hole formed, at the first endportion on the side opposite to the side of the second end portion onwhich the ignition plug is connected, to extend in a direction in whichthe ignition plug is inserted into the plug hole, the sealing member forcovering the air path and the small hole forms a horizontal pathconnecting the air path and the small hole, and the air path extends ina direction in which the ignition coil is inserted into the plug holeand has an end portion connected to the plug hole.
 6. The ignition coilfor an internal combustion engine according to claim 2, wherein the airpath has a stepped or tapered portion at a connection to the small holeto thereby have a cross-sectional area larger than a cross-sectionalarea of the small hole.
 7. The ignition coil for an internal combustionengine according to claim 6, wherein a protrusion is formed of the coilcase to protrude toward the sealing member at an intermediate horizontalportion which is formed at the stepped or tapered portion of the airpath.
 8. The ignition coil for an internal combustion engine accordingto claim 1, wherein a portion around a connection of the air path to theplug hole has a protrusion formed integrally with the coil case toextend toward the side opposite to the side on which the ignition plugis connected.
 9. The ignition coil for an internal combustion engineaccording to claim 1, wherein the outer peripheral wall for forming thespace portion has a protrusion protruding from the outer peripheral wallso as to cover an area around the opening in the space portion.